Stent

ABSTRACT

The invention relates to a stent for transluminal implantation in hollow organs, in particular in blood vessels, ureters, esophagi, colons, duodena, or bile ducts, comprising a substantially tubular body, which can be transferred from a compressed state having a first cross-sectional diameter into an expanded state having an enlarged second cross-sectional diameter, wherein the stent comprises a plurality of cells, which are defined by bordering elements formed by the tubular body. The stent is distinguished in that some of the cells are extended in the longitudinal direction of the stent in comparison with the remaining cells in order to form a slanted end face of the stent.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/746,652, filed Jan. 22, 2018, which is a U.S. National Stage ofInternational Application No. PCT/EP2015/066895, filed Jul. 23, 2015,the entire disclosures of which are incorporated by reference herein.

SUMMARY

The present invention relates to a stent for transluminal implantationinto hollow organs, in particular into blood vessels, ureters, esophagi,the colon, the duodenum or the biliary tract, having a substantiallytubular body which can be converted from a compressed state having afirst cross-sectional diameter into an expanded state having an enlargedsecond cross-sectional diameter, wherein the stent comprises a pluralityof cells which are defined by bordering elements formed by the tubularbody.

Stents of this type are used for the recanalization of pathologicallyaltered hollow organs. In this respect, the stents are introduced in thecompressed state via a delivery catheter to the position within thehollow organ to be treated where they are expanded by different measuresto a diameter which corresponds to the diameter of the healthy holloworgan so that a supporting effect of the hollow organ, for example of avessel wall, is achieved.

Such stents can, for example, be produced in that openings such as slitsare cut into the wall of a tubular body and extend partly in thelongitudinal direction of the stent so that diamond-shaped openings, forexample, are produced on the expansion of the stent. An opening togetherwith its bordering elements is called a cell.

If stents are inserted in proximity to a bifurcation of a hollow organ,stents can be used that have a chamfered end. Such vents provide thepossibility of e.g. supporting a vein at all sides up to thebifurcation, i.e. for example, up to the opening into a further vein.

To be able to ensure their support effect, the stents must be able toexert a sufficient radial alignment force which counteracts a radialforce effect exerted by the vessel wall. This particularly applies inthe region of the chamfered end since the radial placement force istypically reduced there.

It is therefore the object of the present invention to provide a stentof the initially named kind that also provides a high radial placementforce in a chamfered region, whereby a kinking of the stet on itsdeployment is reliably precluded.

This object is satisfied in accordance with the invention by a stenthaving the features of claim 1 and in particular in that some of thecells are formed in elongated form in comparison with the other cells inthe longitudinal direction of the stent to form a chamfered front faceend of the stent.

A chamfered end can be produced due to the elongated cells. In thisrespect, due to the cells elongated in the longitudinal direction, noadditional cells are required to form the chamfered end. It is madepossible by means of the elongated cells also to select a similararrangement of the cells in the chamfered region as in the other tubularbody.

The elongated cells can in particular only be present in a rigid sectionof the stent. In addition, the stent can e.g. comprise a flexiblesection and/or an anchorage section. The following statements withrespect to the elongated cells relate to the rigid section.

A structure of the stent that can provide a particularly high radialplacement force results due to the avoidance of additional cells. It ismade possible in this manner to reliably support blood vessels, forexample, in proximity to bifurcations. A stent in accordance with theinvention can therefore be inserted, for example in the event of venousobstructions in the region of the bifurcation, the confluence of thevenae iliaca communis, into the vena cava inferior, in the upper regionof the vena iliaca communis. The stent can have a diameter of greaterthan or equal to 12 mm for this purpose. The stent can preferably have adiameter between 12 mm and 18 mm.

The dispensing with of additional cells furthermore allows the angle ofthe chamfer to be fixed variably since this angle can be fixed by therelative elongation of the elongated cells.

The chamfered region generally allows a reliable support of the holloworgan up to the bifurcation without, however, e.g. substantiallyprojecting into the blood vessel after the bifurcation.

A cell can be connected to one or more other cells by a connectionsection or by a plurality of connection sections. The length of a cellcan be understood as the spacing in the longitudinal direction betweentwo connection sections, with the respective center of the respectiveconnection section having to be taken into account. A cell comprisessaid cut-out as well as its respective bordering elements, with theconnection sections belonging to the bordering elements.

In a stent in accordance with the invention, at least some of the dellscan be respectively connected to one another by means of a plurality ofconnection sections. Three or four respective connection sections can inparticular be provided in the chamfered region and/or with the elongatedcells. The supporting effect can thus be particularly high due to theradial placement force that can be achieved in this manner.

The stent can be produced from a memory metal that adopts a stored shapefrom a limit temperature onward.

Preferred embodiments of the invention can be seen from the description,from the dependent claims and from the drawings.

In accordance with a first advantageous embodiment, at least some of theelongated cells are arranged along a straight line or an approximatelystraight line that in particular extends in parallel or approximately inparallel with the longitudinal direction. This means that, for example,at least one or two cells arranged after one another on the straightline can be provided. With more than two cells, at least two connectionsections of at least one of these cells can be directly connected to twofurther ones of the elongated cells. Two respective connection sectionsof the elongated cells in particular lie on the straight line.

In accordance with a further advantageous embodiment, the elongatedcells are divisible into a plurality of groups, in particular into ninegroups, with the cells of each group being respectively arranged along astraight line or an approximately straight line and with these lines inparticular extending in parallel or approximately in parallel with thelongitudinal direction. Twelve groups of cells can be provided overallof which nine groups have elongated cells. With such a definition ofgroups, the intermediate spaces between the groups can themselves alsoform cells.

The arrangement of the cells can therefore be selected such that therespective cells are arranged along straight lines or approximatelystraight lines. In addition, the cells can be formed symmetrically toone of these lines. There can therefore in particular be no cellspresent that are inclined or rotated with respect to the other cells. Aweakening of the structure by such rotated cells can be avoided in thismanner.

All the cells within a group can in particular each have the same lengthor approximately the same length viewed in the longitudinal direction.Alternatively, cells having different lengths can also be provided in agroup.

The lines that are formed by the cells of different groups preferablyextend in parallel or approximately in parallel with one another.

A respective equal amount of cells are further preferably provided ineach group from a cross-sectional plane extending perpendicular to thelongitudinal axis up to the chamfered front face end. A radial placementforce can be effected by the provision of a respective equal number ofcells in a group that is substantially constant over the length of thestent. The same number of cells can preferably be provided in each groupin the rigid section of the stent.

Respective angles that can be recognized in the so-called flatprojection of the stent can in particular be formed by the connectionsections of the cells on the use of an equal number of cells. The anglesare defined by the peripheral direction (that is a straight line in theflat projection) and by a straight line, with the straight lineextending through connection sections of the cells. This means that theconnection sections of at least some of the respective cells lie onstraight lines in the flat projection. The angles can be the larger, thecloser the angle is to the chamfered end of the stent, with four, five,or six angles preferably being provided.

The ends of the cells cannot form a straight line in the flat projectionat the chamfered end itself, but can rather define a curve thatapproximates a sine curve. Such a sine curve in the flat projectionresults in a slanted starting cut (the chamfered region) with an exactlyplanar cut surface at the three-dimensional stent.

The cells can be arranged such that a first angle is in a range between20° and 24°, a second angle is in a range between 37° and 44°, a thirdangle is in a range between 48° and 52°, a fourth angle is in a rangebetween 60° and 64°, a fifth angle is in a range between 63° and 67°,and a sixth angle is in a range between 69° and 73°. The largest anglecan in particular be closest to the chamfered end of the stent, whereasthe smallest angle is the furthest away from the chamfered end. Inaddition, an angle of 0° can be provided; this means that a position atthe stent is present in the flat projection at which connection sectionsare arranged along the peripheral direction. The angle of 0° can beprovided at a transition from the rigid region to the flexible region.The cells of a group can be of different lengths to form the describedangles.

It has been found for such a selection of the angles that a very stablestent can be produced in this manner that has a particularly longdurability.

In accordance with a further advantageous embodiment, the length of thecells of adjacent groups falls from a maximum to a minimum in theperipheral direction. Cells having a maximum length are in particulardisposed opposite cells having a minimal length with respect to acentral axis of the stent. The chamfer can be produced by such anarrangement.

At least some of the cells are further preferably connected to oneanother by means of connection sections, with the connection sectionsbetween the elongated cells, in particular only between the longestcells, being formed as elongated. The openings of the longest cells canbe shortened due to the elongated or enlarged connection sections,whereby a uniform bending open of all the cells can be achieved on theexpansion of the stent. Such a uniform bending open can in turn producea uniform distribution of the radial placement force and a particularlyrobust stent.

At least one marker particularly preferably extends in the longitudinaldirection away from the chamfered end, in particular in the form of aneyelet, with the marker having an asymmetrical shape. A marker can be asection of the stent that has an elevated impermeability to X-rays, i.e.is particularly easily visible in an X-ray. The marker can in particularbe an eyelet that is, for example, filled with or covered by tantalum.The marker can also be attached in the chamfered region due to theasymmetrical shape since the marker can extend away from the chamfer.

In other words, the marker can therefore be arranged in a region betweenthe longest and the shortest extent of the stent in the longitudinaldirection. The marker can be deigned as large enough due to theasymmetrical shape to be recognized particularly easily in the X-ray. Inaddition, a further marker can be provided, e.g. at the tip of thechamfer. Yet a further marker can, for example, be attached at thechamfer at a shortest point of the stent.

In accordance with a further advantageous embodiment, at least twoasymmetrical markers are provided at the chamfered end, with the markersin particular being disposed opposite one another with respect to anaxis of the stent. The two markers can therefore be disposedsymmetrically to a plane of the stent that extends through an axis ofthe stent and a tip of the chamfer. The asymmetrical markers can, forexample, be aligned in an X-ray due to such an arrangement. As a result,the position of the stent can be recognized particularly easily in theX-ray.

In accordance with a further advantageous embodiment, the stentcomprises a flexible section that adjoins the rigid section. Theflexible section is disposed opposite the chamfered end. The flexiblesection can have cells that have a larger area in the flat projectionthan cells of the rigid section. The flexible section can be more easilybendable due to the larger cells, whereby the flexible section can beadapted to the shape of extent of a hollow organ in a simple manner. Thecells of the flexible sections can preferably have a tooth-likeboundary.

In accordance with yet a further advantageous embodiment, the stentcomprises an anchorage section that adjoins the flexible section. Thecells of the anchorage section can correspond to the cells of the rigidsection and can, for example, be in diamond shape. The anchorage sectioncan have a small flexibility due to the diamond-shaped cells and canthus fix the stent at its position in the hollow organ. The anchoragesection can form a straight end of the stent to which markers can beattached that extend away from an end of the stent. The markers can havethe shape of eyelets and can likewise e.g. be covered by or filled withtantalum. The stent can be fixed in a delivery catheter by means of themarkers of the anchorage section on the introduction of the stent intothe hollow organ.

The invention furthermore relates to a method of manufacturing a stent,in which method

a) the stent is cut out of a tubular material; and

b) the stent is widened up to its expanded state.

The method in accordance with the invention is characterized in that

c) the shape of the cells of the stent is changed and fixed in theexpanded state.

The individual cells can each be shaped such that a uniform expansionbehavior of the individual cells is achieved by the change of the shapeof the cells. In this manner, the risk of breaking can in particular bereduced with short and medium-sized cells in the proximity of thechamfered region that typically expand asymmetrically and excessivelydue to an inhomogeneous force distribution on expansion.

The acute angles can, for example, be reduced or changed withdiamond-shaped cells having up to four connection sections at therespective corners of the diamond such that they are smaller than 70°,preferably smaller than 60°. This has the result that the stent canbetter withstand larger external forces in the region of the chamferedregion by a homogeneous force dissipation over the structure and therisk of a stent collapse or of a stent break is considerably reduced.

It is moreover possible by means of the method to prevent too wide anexpansion of cells, whereby pre-damage to connection sections can beavoided.

In accordance with an advantageous embodiment, a core to which fasteningmeans are attached is used for widening a core to change and to fix theshape of the cells of the stent. The expansion behavior of theindividual cells can therefore be adapted by the fastening means. Theshape of the cells is consequently changed with respect to the expansionon a use purely of e.g. a cylindrical core. Such a cylindrical core canalso comprise a conical section that facilitates the pulling on of thestent. In addition, the expansion can take place while supplying heat.

The fastening means are particularly preferably needles or mandrels thatare introduced into holes of the core. The needles or mandrels can, forexample, be moved from the interior out of the core or can be pluggedinto the core from the outside. For this purpose, for example, anautomated process can be carried out by means of robots or by means of ahydraulic system, but also a manual adaptation of the cells can becarried out.

In accordance with a further advantageous embodiment, the changed shapeof the cells of the stent is permanently fixed by means of a heatingprocess. Such a fixing is in particular of advantage on the use ofmemory metals that adopt the shape stored by the heating process againon an increase in temperature. A permanent fixing is to be understood asa fixing of the shape of the cells of the stent in the expanded state ofthe stent, with the shape of the cells being maintained in the expandedstate even though the stent has been changed into the compressed statein the interim. On the introduction of the stent into the body, thestent and its cells can, due to body heat, again adopt the shape taughtduring the manufacturing process.

The invention will be described in the following with reference toadvantageous embodiments and to the enclosed drawings. There are shown:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a stent in accordance with the disclosedtechnology in the expanded state in a side view.

FIG. 2 shows the embodiment of the stent of FIG. 1 in the expanded statein a plan view.

FIG. 3 shows the embodiment of the stent of FIG. 1 in a cutrepresentation projected into a plane.

FIG. 4 shows a cut representation the embodiment of FIG. 3 with arepresentation of angles that are defined by connection sections.

DETAILED DESCRIPTION

FIG. 1 and FIG. 2 show a stent 10. The stent 10 has a tubular design andcomprises a rigid section 12, a flexible section 14 adjoining the rigidsection 12, and an anchorage section 16 adjoining the flexible section14.

The rigid section 12 is formed from diamond-shaped (closed) cells 18that are each connected to other diamond-shaped cells 18 via three orfour connection sections 20. The diamond-shaped cells 18 are defined byweb-like bordering elements 22 that are shaped from a metal.

The rigid section 12 comprises a chamfered region 24 that enables theuse of the stent 10 at a bifurcation (not shown) of a hollow organ.

The chamfered region 24 forms an end of the stent 10 and is produced inthat some of the diamond-shaped cells 18 are formed as elongated in alongitudinal direction L. The longest diamond-shaped cells 18 are markedby reference numeral 18 a in the Figures, whereas the shortestdiamond-shaped cells 18 are marked by reference numeral 18 b. Three ofthe shortest diamond-shaped cells 18 b and three of the longestdiamond-shaped cells 18 a are respectively provided in the longitudinaldirection L in the rigid section 12. The longest diamond-shaped cells 18are in this respect disposed opposite the short diamond-shaped cells 18b with respect to a central axis of the stent 10. Three respectivegroups of the longest and shortest diamond-shaped cells 18 a, 18 b areprovided next to one another (i.e. adjacent in the peripheraldirection).

Open cells 26 having a serrated or tooth-like outline are arranged inthe flexible section 14, with respectively fewer open serrated cells 25being provided, viewed in the peripheral direction of the stent 10, asdiamond-shaped cells 18. The flexible section is more easily deformablewith respect to the longitudinal direction L due to the use of feweropen serrated cells 26 and can thus adapt easily to the extent of ablood vessel or similar.

The anchorage section 16 is formed by diamond-shaped cells 18 thatprovide an increased stiffness of the anchorage section 16, whereby thestent 10 reliably maintains its position in a hollow organ.

Four respective eyelet-shaped markers 28, of which a respective threeare visible in FIG. 1, are provided both at the chamfered region 24 andat the end of the stent 10 formed by the anchorage section. All fourmarkers 28 of the chamfered region 24 can be recognized in FIG. 2.

Two of the markers 28 that are attached to the points of the longest andshortest extents of the stent 10 in the chamfered region 24 are formedas symmetrical. Two further markers 28 are attached to the chamferedregion 24 where the stent 10 has its average length. These two markers28 are formed as asymmetrical marks 28 a, with the area of theasymmetrical markers 28 a extending toward the shortest extent of thestent.

FIG. 3 shows the rigid section 12 of the stent 10 of FIG. 1 and FIG. 2in a so-called cut representation. FIG. 3 consequently shows aprojection of cuts in a plane that are introduced into a raw material ofthe stent. A line thus indicates a cut. A plurality of straight cutsextending offset from one another and in parallel can be widened on theexpansion of the stent 10 to form the diamond-shaped cells 18 shown inFIG. 1 and FIG. 2.

The material regions shown as white regions and present between thelines become connection sections 20 or bordering sections 22 after theexpansion. FIG. 3 only shows the rigid section 12 of the stent 10.

It can be recognized in FIG. 3 that extended connection sections 20 aare provided between the longest diamond-shaped cells 18 a and produce amore uniform bending open of all the diamond-shaped cells 18 on theexpansion of the stent.

FIG. 4 shows the view of FIG. 3 with entered angles that are formed byconnection sections 20 having a peripheral direction. Six angles α₁, α₂,α₃, α₄, α₅, α₆ are shown that continuously increase from an angle ofapproximately 22° (α₁) over angles of approximately 40° (α₃), 50° (α₃),62° (α₄), and 65° (α₅) up to an angle of approximately 71° (α₆). Astraight end line 30 that is arranged at the transition from the rigidregion 12 to the flexible region 14 extends in the peripheral directionthrough connection sections 20 and thus defines an angle of 0°.

REFERENCE NUMERAL LIST

-   10 stent-   12 rigid section-   14 flexible section-   16 anchorage section-   18, 18 a, 18 b diamond-shaped cell-   20, 20 a connection section-   22 bordering element-   24 chamfered region-   26 open serrated cell-   28, 28 a markers-   30 end line-   L longitudinal direction-   αangle

1. A method of manufacturing a stent, in which a) the stent is cut outof a tubular material; b) the stent is widened up to its expanded state,and c) a shape of cells of the stent is changed and fixed in theexpanded state.
 2. The method in accordance with claim 1, wherein a coreis used for the widening to which fastening means are attached to changeand to fix the shape of the cells of the stent.
 3. The method inaccordance with claim 1, wherein the fastening means are needles ormandrels that are introduced into holes of the core.
 4. The method inaccordance with claim 1, further comprising the step of d) permanentlyfixing by means of a heating process the shape of the cells of the stentthat is changed.